It is well known in the art that a capacitive or piezoelectric resistive accelerometer comprises a case or housing, a pair of magnetic units including a pair of magnetic structures mounted in the housing, and a flapper or flexure member composed of fused quartz coated with metal. The flapper is interposed between the magnetic units and flexurally mounted relative to the housing. Two coils are respectively mounted on opposite sides of the flapper so as to encircle each of permanent magnets which form part of the magnet unit. As the object or vehicle to which accelerometer is mounted is accelerated, the flapper tends to remain stationary in space, thus moving relative to the magnetic structures. Two capacitors are formed on each side of the flapper and, as the flapper moves relative to the magnetic structures, the capacitance of one of the capacitors increases and the capacitance of the other capacitor decreases. These capacitors are employed in connection with a balance circuit to produce a direct current which is proportional to the acceleration and is fed back to the coils of the accelerometer to restore the flapper.
This type of accelerometer can be used in a portion of aircraft or spacecraft navigation or guidance systems. Accordingly, the temperature in the operating environment of the accelerometer changes over a wide range. Consequently, special care must be taken to the elements of the accelerometer to measure the acceleration with a high accuracy over a wide range of temperature.
In view of the foregoing, U.S. Pat. No. 4,658,647 discloses means for avoiding erroneous factors depending upon a change in ambient temperature from the accelerometer.
Further, for example, U.S. Pat. No. 4,498,342 discloses that another type of accelerometer having a microcircuitry which includes a strain bridge, a preamplifier, a summing amplifier, driver amplifier and a readout resistor. The bridge includes four strain sensitive resistors connected in a bridge circuit and having input terminals energized with direct current, and output terminals giving a direct current bridge signal representative of the deviation of the flexure from its mechanical null.
Even though the accelerometer is constructed to minimize the effects of the temperature change, electronic elements and resistors are considerably affected by it. This conducts the accelerometer to unstability.